The present invention relates to an apparatus for testing rolling contact fatigue resistance of materials with possible interruptions. During rolling contact fatigue resistance of materials testing, an appropriate testing ball is rolled under certain loading and numerous repetitions along the surface of a tested object, while between the ball and the surface of the tested object a point contact is ensured.
It is the aim of the invention to conceive a simple and useful apparatus for testing the rolling contact fatigue resistance of various materials. The present invention enables the interruptions of testing as well as the continuation of testing from a defined prior state.
It is known (e.g., from technical descriptions of available testing systems manufactured by FAG Kugelfischer Georg Schaefer A G) that devices for testing rolling contact fatigue resistance of materials mainly consist of a clamping unit, a loading unit and a driving assembly. The loading unit enables clamping of a testing ball of a predetermined diameter into a clamping area in which the ball can rotate freely and be turned in all directions. The loading unit can be turned so that the clamping area is rotatable around an axis, by which moving the testing ball along a circular path of a pre-defined diameter is enabled. Furthermore, the loading unit ensures the appropriate loading of the testing ball such that the ball is pressed against the corresponding tested object. A driving assembly consists of appropriate driving and bearing parts, which enable turning of the testing ball under loading along the surface of the tested object.
The clamping unit of such a device is arranged to enable firm clamping of a tested object, bearing in mind the loading of the testing ball as well as the movement of the ball along a circular path during testing. The clamping unit has clamps used to prevent movement of the tested object from the clamping unit due to the loading and circular rolling movement of the ball along the surface of the tested object.
Although relatively complicated, such a device enables satisfactory clamping of the tested object during ordinary testing of rolling contact fatigue resistance of materials. However, it is desirable to observe the tested object after subjection to testing. For example, the tested object may be observed after a certain time period has elapsed or after a number of repetitions under loading have occurred in order to make conclusions. Using known devices, the test must be interrupted in order to enable observations and measurements. Another test must then be performed for observation and measurement of the state of the tested object occurring in the next stage.
When using known devices, observation of the state of the tested object after certain stages during testing is possible only by means of several identical tested objects being separately exposed to the same testing up to different stages. In such a manner, the first tested object has to be clamped and thereafter exposed to rolling contact loading for a certain time and for a certain number of repetitions under loading. The tested object must be removed from the clamping unit so that it may be observed and measured. The testing must be repeated using another tested object (e.g., exposed to the same loading for a longer time period), so that more repetitions of loading can be achieved. This approach requires a large number of tested objects to be used and tested, thus resulting in additional time and expense.
Accordingly, an apparatus for testing rolling contact fatigue resistance of materials capable of continued testing after an interruption is provided. The present invention has a driving assembly connected and driven by a loading unit having a testing ball for rolling along the testing surface of each tested object as clamped in the clamping unit. The loading unit has a guide plate, by which at least one rolling position end of the testing ball is unique and repeatably defined, a clamping unit having a clamping area for receiving a tested object, and grooves arranged adjacent thereto for receiving protrusions. The protrusions being smoothly movable along the grooves and attachable in their appropriate positions to prevent movement along each protrusion""s respective groove. In one embodiment of the invention, the guide plate is attached on the bottom side of the loading unit in the direction of the tested object, while the testing ball is at least partially surrounded by a guide plate in the area of its equatorial plane being parallel to the testing surface of the tested object. The guide plate is designed to enable the rolling movement of the testing ball along the tested object in the plane lying parallel to the testing plane in the longitudinal direction such that simultaneous rolling movement of the testing ball in the transversal direction in the same plane is permitted.
Each groove of the clamping plate is equipped with a threaded bore in its bottom. Each protrusion is equipped with a slotted opening extending in the longitudinal direction of its respective groove. Each protrusion is capable of being fixed in an appropriate position within its respective groove while being rested against the tested object by means of a screw. Each screw being inserted through each protrusion""s respective slotted bore and screwed into the belonging screw bore located at the bottom of the protrusion""s respective groove. The clamping plate has at least one slotted bore to facilitate attachment of the plate to an appropriate support.